In AP Micro, taxes and subsidies are government interventions that act as determinants of supply: a tax raises the cost of producing each unit and shifts the supply curve left, while a subsidy is a payment that lowers per-unit costs and shifts the supply curve right.
Taxes and subsidies are two of the government's main levers for changing producer behavior, and in Topic 2.2 they show up as determinants of supply. A tax on producers raises the cost of making each unit, so at every price, firms are willing to supply less. The whole supply curve shifts left. A subsidy is the opposite move. Think of it as a negative tax, a coupon the government hands producers for every unit they make. Costs fall, and the supply curve shifts right.
The key graphing skill is recognizing that these are shifts of the entire curve, not movements along it. A change in the good's own price moves you along the supply curve (a change in quantity supplied). A tax or subsidy changes the conditions of production itself, so it relocates the whole curve (a change in supply). Later in Unit 2 you'll layer on the consequences, like how a per-unit tax raises the equilibrium price, shrinks quantity, and creates deadweight loss.
Taxes and subsidies live in Unit 2: Supply and Demand, Topic 2.2 (Supply), supporting learning objective AP Micro 2.2.C, which asks you to explain how producers respond to changes in incentives using graphs. The essential knowledge is direct about it. Changes in the determinants of supply cause the supply curve to shift, and taxes and subsidies are textbook examples of those determinants. They're also the connective tissue of the whole course. The same logic from Topic 2.2 powers tax incidence and deadweight loss analysis later in Unit 2, per-unit versus lump-sum taxes on firm cost curves in Units 3-4, and corrective taxes and subsidies for externalities in Unit 6. If you can shift a supply curve correctly here, you've set up half the graphs on the exam.
Keep studying AP Microeconomics Unit 2
Determinants of Supply (Unit 2)
Taxes and subsidies are members of this family. Anything that changes production costs without changing the good's own price (input prices, technology, taxes, subsidies, expectations) shifts the supply curve rather than moving along it.
Market Equilibrium (Unit 2)
A tax or subsidy doesn't just move one curve, it moves the whole market outcome. Tax shifts supply left, so equilibrium price rises and quantity falls. Subsidy shifts supply right, so price falls and quantity rises. Trace both effects on every graph.
Deadweight Loss (Unit 2)
When a per-unit tax pushes quantity below the free-market equilibrium, some mutually beneficial trades stop happening. That lost surplus is deadweight loss, and it's the standard follow-up question after you've drawn the tax shift.
Supply Curve (Unit 2)
The supply curve is the canvas all of this happens on. The market supply curve sums up individual sellers' supply, and a tax effectively makes every seller behave as if their costs jumped, so the entire summed curve relocates left.
On multiple choice, taxes and subsidies usually appear as a 'what shifts supply?' question. A stem describes a new excise tax or a government subsidy and asks you to predict the curve shift and the new equilibrium price and quantity. Fiveable practice questions test them alongside the other determinants of supply, so know the full list and which direction each one shifts the curve. On FRQs, the move is graphical. You draw a correctly labeled supply and demand graph, shift supply left (tax) or right (subsidy), and identify the new equilibrium. In later units, the stakes rise. You may need to show the deadweight loss from a per-unit tax, distinguish a per-unit tax (shifts MC and supply) from a lump-sum tax (only shifts average costs), or recommend a per-unit subsidy to fix a positive externality in Unit 6. The Topic 2.2 version is the foundation for all of those.
A per-unit tax charges firms for every unit produced, so it changes marginal cost and shifts the supply curve, reducing output. A lump-sum tax is a flat fee no matter how much the firm produces, so it leaves marginal cost (and the supply curve) alone and only changes the firm's fixed costs and profit. In Unit 2, taxes that shift supply are per-unit taxes. Mixing these up is one of the most common point-losers when this idea returns in Units 3-4.
A tax on producers raises the cost of each unit, so the supply curve shifts left and quantity supplied falls at every price.
A subsidy works like a negative tax, lowering per-unit production costs and shifting the supply curve right.
Taxes and subsidies cause shifts of the supply curve, while a change in the good's own price causes only a movement along the curve.
After a tax shifts supply left, equilibrium price rises and equilibrium quantity falls; a subsidy does the reverse.
A per-unit tax changes marginal cost and shifts supply, but a lump-sum tax does not shift the supply curve at all.
This same shift logic returns in Unit 6, where corrective taxes and subsidies are the standard fixes for negative and positive externalities.
They're government interventions that act as determinants of supply. A tax raises production costs and shifts the supply curve left, while a subsidy lowers costs and shifts it right, which is exactly what learning objective AP Micro 2.2.C asks you to show on a graph.
It shifts the entire curve. Movements along the supply curve only happen when the good's own price changes. A tax changes production costs at every price, so the whole curve relocates left.
Yes, it depends on who pays. A tax collected from producers shifts supply left, while a tax collected from consumers shifts demand left. In Topic 2.2 the focus is the producer side, but the equilibrium effects on quantity end up the same either way.
A per-unit tax charges the firm for every unit made, so it raises marginal cost and shifts the supply curve left. A lump-sum tax is a one-time flat fee, so it changes profit but not marginal cost, and the supply curve doesn't move.
Pretty much, yes. A subsidy shifts the supply curve right instead of left, dropping the equilibrium price and raising the equilibrium quantity. If you can graph a tax, mirror the shift and you've graphed a subsidy.